voters there held a referendum in march, and decided to join russia. then, president vladimir putin annexed the republic. he's accused of sending in arms and agents to fuel the unrest so he could eventually send in troops under the pretense of protecting ethnic russians. putin and members of his administration have denied that again and again. he said in a statement that ukraine must withdraw all military units from the southeast, stop the violence, and immediately start a national dialogue that would involve all regions and all political forces. ukrainian soldiers have been manning checkpoints on the outskirts of the occupied area. but in the capital, they held an exercise to test the response to a threat on a government building. the head of the state guard said they performed a task well. farther west, police and volunteers set up checkpoints on roads leading to leveu. they're trying to prevent pro-russian separatists from entering the city. residents know it's unlikely this will reach their doorstep. but it's another sign many in ukraine are worrie